I think flipflops are certainly more prone to the nasties, especially wearing them in the city. Indulge me in a rant:
I absolutely believe everything reported hear about a pair of NYC flipflops being germy and disgusting. First of all, most flipflops have a very thin sole. Some of them like Tevas and other more substantial sandals are thicker, but that is not what most people wear here. The sandals I see here are extremely flimsy. The foot doesn't even always come back down on squarely on the sole. The lack of ankle support means the foot just sort of flops around any which way, sometimes slightly missing the sole and touching the ground. I don't personally care if they are rubbery flipflops or "fancy" leather flipflops. They are equally gross.
It is absolutely NASTY seeing how the soles of flipflop wearers' feet look after a day around the city. It really nauseates me to think about having only a thin piece of rubber between my foot and the subway or the restroom floor at Penn Station. My roommates in college were all regular flipflop wearers and it really grossed me out to see their dirty footprints embedded into their flipflops. I think a sandal where your foot is securely attached to the sole and has even a little bit of elevation from the ground are probably more hygienic--I certainly never found dirt-encrusted footprints in my Brulees, which I always wear when I'm in the city now. Even a thong sandal with a slightly thicker sole and an ankle strap is a good alternative. The tiny wedge heel of my Brulees, along with the secure straps seem to do the trick. I think a thin sole CAN work provided the foot is strapped in securely and there is no spillage while walking...but I still do not prefer it. All those uber flat gladiators also rub me the wrong way, so it isn't just a question of style and snobbery.
ANY open footwear is going to leave you more prone to germs and bacteria than a closed shoe. I am not a germophobe or a hypochondriac. New York is a hot city where people move a lot and open footwear is more than reasonable in the summer. But I think people need to seriously use some more common sense. Flipflops are beachwear. They are meant for walking in sand, so that the sand can pass through and not get trapped the way it would in other shoes. But that same purpose makes them utterly wrong for walking through an urban area.
And don't get me started on all the orthopedic problems of flipflops...
